I can make a much stronger argument that if anything the reindeer antlers don't match while the candy cane recall does. Quite simply examine Kat's outfit. The primary color scheme is red/white/green, traditional holiday colors. The only brown in that outfit is the antlers. So already having a candy cane matches the color scheme. But let's examine the outfit further, her armsleeves and stockings are red and white in the same pattern of, that's right, a candy cane. So her own clothing accents the outfit as a whole. So it would make sense that it would benefit the outfit more to remove the antlers instead.
I could also go with the argument that in terms of snowdown theme that Kat matches the consistency of Riot's previous snowdown works. In previous snowdowns you have always had four categories made. The Santa skin, the scary skin, the fun skin, and finally the sexy skin. You can look back and it has always been like this. This year it's quite simple that Riot was consistent.
Kat's skin is of the same style as previous sexy skins who were previously Nidalee(snow bunny), MF(candy cane), Leblanc(Mistletoe) and now Kat.
As for Morello's argument. Well that is easily debunked because his examples have always consisted of designs that actually were never developed or patched on the PBE. So while he talks about a halloween skin throwing xmas trees it ignores the fact that Riot is a business and they have procedures. So this isn't a hypothetical situation he gets to debate. The debate is on a skin, and recall animation that was physically created. Which means animators had to create the concept art. Designers had to create the 3d model, and through all of Riot's meetings(to which they BRAG about that in the forums) it had to of been approved by not only other rioters but also their lead designers and artists. For all that time, money, and constant approval there was a physical product created.
So logically there is only one possible reason why to remove the animation so quickly. Social pressure.
One final note though. Kat and many other champion's current recall animations are just as erotic. Because if you examine and compare her recall animations her original is just as erotic. The xmas skin had her spin around a candy cane and then she arches her back looking up. Now, think about her original, what does she do? She gets on her knees, and arches her back and looks up to the sky. Let me retype that, she gets on her KNEES and then arches her back and looks up to the sky. So the only difference is the spin around the candy cane. So the only reason people could be offended is through object identification because they are unable to perceive the current recall animations as erotic.